1. Field of the Invention
The present invention relates to computer-implemented systems and methods for drawing images, and in particular to a computer-aided drafting tool for drawing lines at pre-settable angles from an existing linear entity and at pre-settable distances from pick points on the existing linear entity.
2. Description of the Related Art
Computer Aided Design (CAD) and other drawing programs allow the preparation and editing of machine drawings, schematic drawings, and artwork. Typically, the user creates these drawings with the use of a library of objects and a number of drawing tools. These drawing tools allow the user to define and edit lines, polygons, ovoids, and other shapes.
One useful feature in such drawing programs is the ability to snap lines, and shapes to certain global coordinate frames. An example of such a system is the polar coordinate snap tool disclosed in U.S. Pat. No. 5,793,377, issued to Moore on Aug. 11, 1998, which is hereby incorporated by reference herein. This snap tool allows the user to specify a polar coordinate snap angle and length to which all future lines will be constrained.
However, in prior systems, the polar coordinate snap angle and length is referenced to a fixed (x,y) Cartesian coordinate frame, and hence only permit the drawings to snap to a coordinate frame that is globally applied to an entire drawing. No provision is made to constrain a new line to a specified geometrical relationship (such as a relative angle) with an existing line. This deficiency limits the usefulness of the conventional polar snap tools. What is needed is a tool that allows the user to draw new lines with specific, pre-defined geometrical relationships with existing lines. The present invention satisfies that need.